[clang] [clang][Interp] Integral pointers (PR #84159)

[Aaron Ballman via cfe-commits]

================
@@ -187,6 +195,34 @@ bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
     return true;
   }
 
+  case CK_IntegralToPointer: {
+    QualType IntType = SubExpr->getType();
+    assert(IntType->isIntegralOrEnumerationType());
+    if (!this->visit(SubExpr))
+      return false;
+    // FIXME: I think the discard is wrong since the int->ptr cast might cause a
+    // diagnostic.
+    PrimType T = classifyPrim(IntType);
+    if (DiscardResult)
+      return this->emitPop(T, CE);
+
+    QualType PtrType = CE->getType();
+    assert(PtrType->isPointerType());
+
+    const Descriptor *Desc;
+    if (std::optional<PrimType> T = classify(PtrType->getPointeeType())) {
+      Desc = P.createDescriptor(SubExpr, *T);
+    } else if (PtrType->getPointeeType()->isVoidType())
+      Desc = nullptr;
+    else {
+      Desc = P.createDescriptor(CE, PtrType->getPointeeType().getTypePtr(),
+                                Descriptor::InlineDescMD, true, false,
+                                /*IsMutable=*/false, nullptr);
+    }
----------------
AaronBallman wrote:

```suggestion
    if (std::optional<PrimType> T = classify(PtrType->getPointeeType()))
      Desc = P.createDescriptor(SubExpr, *T);
    else if (PtrType->getPointeeType()->isVoidType())
      Desc = nullptr;
    else
      Desc = P.createDescriptor(CE, PtrType->getPointeeType().getTypePtr(),
                                Descriptor::InlineDescMD, true, false,
                                /*IsMutable=*/false, nullptr);
```

https://github.com/llvm/llvm-project/pull/84159